Hi, since you will arrive at Beijing airport and your wife use wheel Chair, I suggest you stay in a hotel at the city center of Beijing which would owns very convenient transportation. Think about Beijing Red wall Garden Hotel which is situated in Dongcheng District, Beijing, and close to Wangfujing Avenue.
Thus, you can take the airpore express train from the airport to Dongzhimen and then take a taxi to the hotel. You need to pay the transport with RMB.